Treament of surfaces of aluminum or alloys of aluminum in order to prepare them for receiving a metallic deposit.



STATES PATENT. OFFICE.

rnANcoIs nu'eus'rn ROUX,

or PARIS, ERANCE, ASS-IGNOR'TO socrn'rn rnauoars, or rams, rnanon.

TREATMENT OF SURFACES OF ALUMINUM OR ALLOYS F ALUMINUM IN ORDER- TO NoDrawing. I

- To all whom it may concern Be it known that I, FRANgoIs AUeUs'rE Roux,a citizen of the Republic of France, and resident of Paris, France, haveinvented new and useful improvements relating to the treatmentofsurfaces of aluminum or alloys of aluminum in order to prepare them forreceiving a metallic deposit, which are fully deposited on the saidsurface. To overcome this difiiculty various methods have already beenproposed. One of the processes consistsin submitting aluminum to theaction of baths which precipitate, on its surface,-

heavy metals having for object .to prevent its oxidation. According toanother method,

and with the same end in view, a solution of a' neutral metallic fluorid.is employed in a neutral alkaline salt derived from an or *ganic acid.It is also possible to bring consecutively into action both thesolutions, by beginning with the first named. However these processeshave the disadvantage of leaving on the aluminum, at the moment when itintroduced. into h the galvanic baths, a pulverulent deposit whicha'rinsing and even a brushing are not able to remove,

and which. a passage through an acid bath would wholly eliminate,leaving the oxidized met-a1 bare. hlnsuch .instance, perfect adherenceof the metals to be deposited is im possible. If placed into the bathswith the pulverulent deposit, the deposits are rough and lend themselvespoorly to polishing, and

at the same time theyare liable to disappear at certain points'in theelectrolytic baths,

from which there, results an incomplete ad-.

herence ofthe deposited metal.

The present process consists n submitting the aluminum surfaces,previously cleansedby any known means, to the action of dilutedhydracids or of diluteda'lkalis,

ity to the to whichhas PREPARE THEM FOR RECEIVING- A METALLIC DEIQSIT.

Specification of Letters Patent. Patented J 11119 22, 1915 Applicationfiled J'anuaryw, 1914. Serial No. 813,052.

been added a salt of tin or of another soluble I metal; then, afterrinsing the said surfaces are passed through a salt solution that iscapable of fixing on them the tin or other metal and at the same time ofexpelling the hydrogen which was inclosed in the pulverulent metallicdeposit formed on the aluminum. The aluminum salts and the alums inasaturated and more or less warm solution reali'ze particularly wellthis latter condition, all the more asthey have the property ofdissolving the metallic oxids, which is very advantageous for theperforming of the process. W

In carrying out the present invention, the aluminum surface to be coatedis cleansed by any method, for instance by a solution ofsoda or potashat about 5%, Whihh is preferably employed when l 'ot; then the lasttraces of alkali are washed away or neutralized, if

LALUMINIUM necessary, in a bath of diluted sulfuric or.

nitric acid, or in a mixture of both these acids; after that, the metal,having first been thoroughly rinsed in water, is immersed in a dilutedsolution of a hydracid or an alkaline hydrate at about 5 degrees Baum,to which is added a salt of tin or of another soluble metal. Forinstance tin chlorid in the proportion of 1% gives good results.

The articles are then quickly and thoroughly rinsed, after which theyare immersed into a saturated solution, preferably in a heated 'state,of 'an aluminum salt. Ammonia alum isespeciall'y to;be' recommended-During the operation the hydrogen inclosed in the layer of soluble metaldepositedon the aluminum escapes violently and atthe same time itremoves mechanically the pulverulent deposit which is in excess, itprevents the oxidation of aluminum and gives tenactin or heavy metaldeposit. The

aluminum. after having been so treated is .then rinsed,'and subsequentlyimmersed'in a solution "of a diluted mineral acids1 1lfur ic ornitr1cthe'efi'ect thereof conslsting 1H dissolving the last traces ofthe metallic precipitate of*which' the adherence would not be sufficientto ofi er-a proper resistance to the electrolytic baths. Ihelatteroperation is notabsolutely indispensable. -.Having been rinsed,thealuminum is readyto receive allelectrolytiOdePosits. It also may bekept in abeyance in pure Water, or it may be dried. In any case itssurface will not become oxidized and will always remain fit to receive ametallic deposit.

l/Vhat I claim is: e r 1. A process of treating surfaces of aluminum orits alloysto prepare-them for receiving a metallic deposlt, whichconsists in subjecting the previously cleansed surfaces to the action ofa weakbath containing a hydrac'id holding a .soluble metal in solution,

- thereby to precipitatea dep sit of said soluble metal upon saidsurfa'stand to liberate'hydrogen which remains occluded in the depositwhere it adheres to said surfaces,

rinsing said surfaces, and passing the surfaces through a hot bathconstituted by a saturated solution of a salt capable of expelling theoccluded hydrogen and of fixing on saidsurfaces thesoluble metalemployed.

2. A process of treating surfaces of aluminum or its alloys to preparethem for receiving a metallic deposit; which consists in sub- 7 Jectingthe previously cleansed surfaces to the action of a weak bathcontaininga hydracid holding'tin in solution, thereby to precipitate .adeposit of tin upon said surfaces and to liberate hydrogen which remainsoccluded. in the deposit where it adheres tosaid surfa'ees, rinsing saidsurfaces, and passing :the surfaces through a hot bath constituted by {asaturated solution of a salt capable of expelling the occluded hydrogenand offixing the tin on said surfaces.

3. A process of treating surfaces of aluminum or its alloys to preparethem for receiv-' ing a metallic deposit, which consists in subjectingthe previously cleansed surfaces to the action of a weak bath containinga hydracid holding tin in said surfaces, and passing them through asolution, rinsing hot bath constituted by a saturated solution of analuminum salt. 4. A process of treating surfaces of aluminum or itsalloys to prepare them for receiving a metallic deposit, which consists-1n sub ecting the previously cleansed sur faces to the action of a weakbath containing a substance holding a soluble metal in solution, therebyto precipitate a deposit of said soluble metal upon said surfaces and Yto liberate hydrogen which remains occluded 1n the deposit where 1tadheres to sald surfaces, rinslng said surfaces, and passing thesurfaces through a hot bath constituted by a saturated solution of asalt capable of expelling the occluded hydrogen and of fixing on saidsurfaces the soluble metal employed.

Y 5. A process of treating surfaces of alumi num or its alloys toprepare them for receiving a metallic deposit, which consists insubjecting the previously cleansed surfaces to the action of a weak bathcontaining a hydracid holding a soluble metal .in solution, therebytoprecipitate a deposit ofsaid solube metal upon said surfaces and toliberate hydrogen which remains occluded in the deposit where it adheresto said surfaces, rinsing said surfaces, passing the surfaces through ahot bath constituted by a saturated solution of a salt capable ofexpelling the occluded hydrogen and of fixing onsaid surfaces thesoluble metal employed, and

